For a customer relying on computing systems provided by a computing resource service provider for operation of the customer's business, the occurrence of a large-scale event that renders one or more of the computing systems inoperable, such as a power, thermal, or network failure, can have adverse consequences to the customer's business. Often, the customer and/or the computing resource service provider may not even become aware of the occurrence of the large-scale event until clients of the customer register complaints about difficulty in accessing the customer's computing systems, and an investigation is conducted by the computing resource service provider to determine the cause of the complaints. Furthermore, because determination of the occurrence of a large-scale event may depend on various factors, such as a number of affected computing systems, number of customers affected, extent of customers' reliance on the affected computing systems, and services provided by the affected computing systems, proactively detecting the occurrence of a large-scale event can be difficult.